[Feature]: Add granular SIP call + transfer lifecycle webhook events for CRM workflows

[nilay-automatesmb]

Problem statement

Rapida currently emits conversation-level webhook events (conversation.begin/completed/failed and endpoint-api events), but CRM systems need lower-level telephony lifecycle visibility before and around conversation startup.

For SIP call-center workflows, downstream systems must:

• create exactly one backend call session per provider call_id
• avoid duplicate contact lookup/create caused by multiple browser clients reacting independently
• notify intended users on transfer attempts
• close stale notifications when another target answers
• track final outcome for each attempted target (connected/no_answer/busy/rejected/cancelled/failed)

Without granular SIP/call-routing events, CRM disposition and real-time routing UX are incomplete.

Proposed solution

Extend the existing SIP webhook pipeline (server-to-server, same webhook executor path) with additional lifecycle events and normalized outcomes.

Add/extend events:

• Call lifecycle: call.created, call.ringing, call.answered, call.no_answer, call.busy, call.rejected, call.cancelled, call.ended, call.failed
• Transfer lifecycle: transfer.requested, transfer.attempt.started, transfer.connected, transfer.attempt.ended, transfer.cancelled, transfer.failed
• Define (but only emit with reliable hooks): call.media.started, transfer.target.ringing

Emission semantics:

• call.created before/around ringing once SIP session identity is established
• call.ringing around 180 Ringing
• call.answered around 200 OK / connected
• classify known SIP failures into call.no_answer / call.busy / call.rejected; keep call.failed for unclassified/technical failures
• transfer.requested before per-target attempts
• transfer.attempt.ended for every attempted target terminal outcome
• transfer.cancelled for pending targets when another target answers (reason=answered_by_other)

Non-goals:

• no browser websocket implementation
• no separate realtime server
• no broad SIP refactor

Alternatives considered

No response

Impact area

None